This invention relates to compression release engine brakes, and more particularly to improvements to compression release engine brakes of the general type shown, for example, in Meistrick et al. U.S. Pat. Nos. Re. 33,052 and 4,838,516, both of which are hereby incorporated by reference herein.
The above-mentioned Meistrick et al. patents show compression release engine brakes in which, during operation of the engine brake, master hydraulic pistons reciprocated by intake and/or exhaust valve actuating mechanisms in an associated internal combustion engine pressurize the hydraulic fluid in a hydraulic subcircuit against the resilience of additional hydraulic fluid in a plenum. At a predetermined time during the stroke of one of the above-mentioned master pistons, the piston opens a trigger valve which allows the pressurized hydraulic fluid in the above-mentioned subcircuit to flow to a slave piston cylinder. This causes a slave piston in that cylinder to reciprocate, thereby opening an exhaust valve in the internal combustion engine near top dead center of the compression stoke of the engine cylinder served by that exhaust valve. Compressed air in that engine cylinder is thereby released to the exhaust manifold of the engine so that the engine does not recover the work of compressing that air during the subsequent expansion stroke of the engine cylinder. (The engine's fuel is cut off during operation of the engine brake.) The engine brake therefore operates to temporarily convert the engine from a power source to a power-absorbing air compressor. This greatly increases the braking available from the engine to slow down a vehicle propelled by the engine. The need to use the vehicle's wheel brakes is therefore reduced, thereby prolonging wheel brake life and increasing the safety of operation of the vehicle.
While engine brakes of the type shown in the above-mentioned patents work extremely well and have been highly successful, they do involve relatively complex mechanical and hydraulic components. These components are relatively costly and require careful adjustment to achieve the desired precise timing of engine exhaust valve openings. It is also generally difficult or impossible to cause these components to adapt to different engine operating conditions in order to optimize the performance of the engine brake at different engine operating conditions. The engine brake is typically adjusted so that its performance is optimum at one set of operating conditions (e.g., at one engine speed), thereby leaving performance less than optimum at other operating conditions.
In view of the foregoing, it is an object of this invention to improve and simplify compression release engine brakes of the type described above.
It is another object of this invention to improve and optimize the performance of engine brakes of the type described above at all engine speeds and other variable engine operating conditions.
It is still another object of this invention to eliminate the relatively complex mechanical triggering of compression release events in engine brakes of the type described above.
It is yet another object of this invention to provide compression release engine brake apparatus that is simpler to install and adjust, and which can be more easily made to maintain its initial or "design" operating characteristics.
It is still another object of this invention to provide compression release engine brake apparatus which can interface with other apparatus such as engine and vehicle sensors and which can provide various types of programmable braking operation.